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Aims: The variability patterns of fern root characteristics have seldom been studied. Here we explored variability in root morphology, histology and chemistry among fern species of temperate forest, and compared the observed patterns with those of seed plants. Methods: We sampled nine herbaceous fern species from temperate forest in northeastern China, and measured root morphological, histological and chemical characteristics across branch orders for each species. Results: All nine fern species had 3 or 4 root orders. With increasing root order, diameter, tissue density, cortical thickness and vascular cylinder diameter increased, while specific root length (SRL) and tissue nitrogen concentration decreased. These were similar to the variability patterns that have been reported for seed plants, except for cortex. Like seed plants, nine fern species showed close relationships among root morphological, histological and chemical characteristics in first-order roots, such as diameter and cortex, tissue density and nitrogen concentration, suggesting that the general linkage between root structure and function exists in all vascular plants. Conclusions: The observed variation within fern root systems is comparable to the reported variation in seed plants, indicating that the same functional constraints control the evolution and development of root systems in vascular plants belonging either to the fern or seed plant lineages. [ABSTRACT FROM AUTHOR]

Determining which kinds of roots are likely to be consumed by root herbivores may improve our understanding of the mechanistic control on fine root dynamics. Here, we tested the hypothesis that root herbivores prefer to consume the distal lower order roots in their branching networks. Insecticide was applied to soil to quantify effects of root herbivores on root biomass and production in the first five orders (the distal roots numbered as first-order) in Fraxinus mandshurica and Larix gmelinii plantations from May 2008 to July 2009. Root morphology, chemistry, anatomy and physiology were measured simultaneously across branching orders. Among the first five order roots, significant consumptions by herbivores were found only for the two distal lower order roots throughout growing seasons, with 62% of biomass and 57% of production for F. mandshurica, and 71% and 79% for L. gmelinii, respectively. Our results suggest that the distal lower order roots are more palatable and attractive to root herbivores in both plantations, probably because they have higher tissue N, greater respiration rates and lower cellulose. Thus, overlooking herbivore consumption may lead to large underestimation in root biomass and production, which are critical in determining C budget and nutrient cycles in forest ecosystems. [ABSTRACT FROM AUTHOR]

We have limited understanding of architecture and morphology of fine root systems in large woody trees. This study investigated architecture, morphology, and biomass of different fine root branch orders of two temperate tree species from Northeastern China— Larix gmelinii Rupr and Fraxinus mandshurica Rupr —by sampling up to five fine root branch orders three times during the 2003 growing season from two soil depths (i.e., 0–10 and.10–20 cm). Branching ratio ( R b) differed with the level of branching: R b values from the fifth to the second order of branching were approximately three in both species, but markedly higher for the first two orders of branching, reaching a value of 10.4 for L. gmelinii and 18.6 for F. mandshurica. Fine root diameter, length, SRL and root length density not only had systematic changes with root order, but also varied significantly with season and soil depth. Total biomass per order did not change systematically with branch order. Compared to the second, third and/or fourth order, the first order roots exhibited higher biomass throughout the growing season and soil depths, a pattern related to consistently higher R b values for the first two orders of branching than the other levels of branching. Moreover, the differences in architecture and morphology across order, season, and soil depth between the two species were consistent with the morphological disparity between gymnosperms and angiosperms reported previously. The results of this study suggest that root architecture and morphology, especially those of the first order roots, should be important for understanding the complexity and multi-functionality of tree fine roots with respect to root nutrient and water uptake, and fine root dynamics in forest ecosystems. [ABSTRACT FROM AUTHOR]